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Few of us relish the idea of opening windows during frigid winters just to air out our homes and let in a little fresh air, but keeping our homes sealed up can also keep dangerous indoor air pollutants from escaping. Fortunately, reducing your exposure to harmful gases without freezing to death is easy if you know where to look.

Where You'll Find Them

Combustion gases like carbon monoxide, nitrogen dioxide, benzene and toluene come from leaking or improperly vented gas and wood-burning stoves, fireplaces, oil-burning furnaces and attached garages. These gases can cause headache, fatigue, flu-like symptoms and, in severe cases, death.

Winter is also a good time to check your home for radon, a colorless, tasteless gas that forms as naturally occurring uranium decays in soil and water. Radon is the second-leading cause of lung cancer in America, and the Environmental Protection Agency (EPA) estimates that one in every 15 homes nationwide has elevated levels of radon. Radon comes from the ground, and levels are usually highest in basements and anywhere you have holes or cracks in your home's foundation.

What You Can Do

If you're contemplating the purchase of a ventilator and a HAZMAT suit, don't worry. These gases are easy to eliminate with a few simple steps.

*Every home should have combination CO/smoke alarms, but don't rely entirely on a detector to catch the problem. Maintain your appliances to keep them from leaking, ensure proper ventilation whenever using a fireplace and gas- or wood-burning stove, and have your chimneys and vents assessed by a reputable heating contractor or your utility company

*Inexpensive radon testing kits are available at home improvement stores; if you find levels between 2 and 4 pCi/L, call a professional. The website for the National Radon Safety Board lists radon-remediation professionals by state (www.nrsb.org). Ensuring that your home is properly ventilated and that foundation cracks are sealed will help keep the gas levels down.

*Ban cigarettes from your home. Secondhand smoke contains many of the hazardous gases listed above.

*Attach a door sweep to doors that lead to attached garages. These will help cut down on combustion gases that come from automobile exhaust.

*Open your windows when the temperatures outside are bearable. The more air exchange you have, the lower the levels of gases.